1. Field of the Invention
The present invention relates to a technique to manufacture a quartz-crystal resonator using, for example, an AT cut quartz-crystal piece having an anisotropy.
2. Description of the Related Art
As a reference source of frequency and a reference source of time in an oscillator or the like, which is one of electronic components, a quartz-crystal resonator is used. A quartz-crystal piece of the quartz-crystal resonator is formed in a predetermined shape, which is, for example, a rectangular parallelepiped shape, from a wafer of a quartz-crystal that is AT cut, for example, and a large number of the quartz-crystal pieces are formed from the single wafer.
As one example of a method of forming the above quartz-crystal piece, as illustrated in FIG. 13(a) and FIG. 13(b), for example, there is a method in which etching masks 106 are formed on a front surface 5c and a rear surface 5d of a quartz-crystal wafer W1, and by etching the quartz-crystal wafer W1, a desired quartz-crystal piece 110 corresponding to shapes of the etching masks 106 is obtained. When the quartz-crystal piece is formed by etching, quartz-crystals at portions under the etching masks 106 are etched by side etching. Thus, the etching masks 106 have sizes and the shapes thereof determined by considering etching amounts (amounts in which quartz-crystals are etched) by side etching.
However, a quartz-crystal has an anisotropy and has a characteristic that etching proceeds aggressively on one side in a specific crystal axis direction, and in the AT cut quartz-crystal, due to an anisotropy thereof, etching proceeds aggressively on a +X side in an X axis direction being a crystal axis in particular. Thus, when the quartz-crystal piece 110 is tried to be formed by using the etching masks 106, the quartz-crystal piece 110 in a deformed shape having chipped portions S1 at corners on the +X side is formed as illustrated in FIG. 14(a) and FIG. 14(b), and therefore there is a case that a desired quartz-crystal piece cannot be obtained.
When the shape of the quartz-crystal piece is deformed, a characteristic of the quartz-crystal resonator is deteriorated in forming excitation electrodes and lead electrodes on the quartz-crystal piece, and thus it is not preferable that the corners of the quartz-crystal piece are side etched. When the quartz-crystal piece is made small in particular, a difference in sizes between the quartz-crystal piece and the excitation electrodes is made small. Thus, if the chipped portions exist in the quartz-crystal piece, it can be considered that the excitation electrodes are formed at the chipped portions. Then, when the excitation electrodes are formed at the chipped portions, there is a concern that an effect on the characteristic of the quartz-crystal resonator is made large.
On the other hand, in Patent Document 1, there is disclosed a method of manufacturing a quartz-crystal resonator, in which support portions connecting a quartz-crystal piece to a quartz-crystal substrate and supporting the quartz-crystal piece and the quartz-crystal substrate are provided at both corner portions on a −X side of the quartz-crystal piece to be formed, and the support portions prevent chipped portions from being formed at corners on the −X side of the quartz-crystal piece. Further in Patent Document 2, there is disclosed a method of manufacturing a quartz-crystal resonator, in which support portions connecting a quartz-crystal piece to a quartz-crystal substrate and supporting the quartz-crystal piece and the quartz-crystal substrate are provided at both corner portions on a +X side of the quartz-crystal piece to be formed, and the support portions prevent chipped portions from being formed at corners on the +X side of the quartz-crystal piece.
In the method in Patent Document 1, connection support portions are not formed on a +X side, and thus side etching cannot be prevented when the quartz-crystal piece is formed from an AT cut quartz-crystal wafer. In the method in Patent Document 2, when the quartz-crystal piece is formed from an AT cut quartz-crystal wafer, etching in the corner portions on the +X side is prevented by connection support portions, and therefore generation of side etching can be prevented. However, on a connection support portion side, a shape of the quartz-crystal piece is deformed when the quartz-crystal piece is cut, and therefore it is general that lead electrodes are not formed on the connection support portion side. In the method in Patent Document 1, lead electrodes are to be definitely formed on the +X side, so that there is a difficult point that a layout of the electrodes in the quartz-crystal resonator cannot be performed without restraint.
Accordingly, since the method of manufacturing the quartz-crystal resonator, which is illustrated in FIG. 13(a) and FIG. 13(b), is more advantageous to manufacture with regard to a point on which it is possible to select without restraint where on the quartz-crystal piece a connection support portion is formed, a method of manufacturing a quartz-crystal resonator, in which a connection support portion is formed at an arbitrary place and a desired quartz-crystal piece can be obtained by etching, is required.    [Patent Document 1] Japanese Patent Application Laid-open No. 2008-92505 (paragraphs 0016, 0018)    [Patent Document 2] Japanese Patent Application Laid-open No. 2007-142526 (paragraphs 0015, 0019)